M-Jet 30 - 3D Printable Jet Drive for RC Boats

M-Jet 30 - 3D Printable Jet Drive for RC Boats 3D print model

Complete propulsion system for RC Boats.

You get 12 STL files for 12 parts of the jet drive, designed to be FDM 3D printed with no supports. You get 12 STL files for 12 parts of the jet drive, designed to be FDM 3D printed with no supports. You get 12 STL files for 12 parts of the jet drive, designed to be FDM 3D printed with no supports. You can assemble it and install it into your RC boat.

The f3d files, STEP files or any similar CAD format is not included. I cannot share it for various reasons.

COMPLETE PDF MANUAL: https://drive.google.com/open?id=10guq2Laz8EfP5fF6TGrs1q0CErPBnrqk

Includes part list, print settings, assembly and installation guide.

M-Jet 30 features:

2-stage configuration, meaning it has 2 impellers and 2 sections of stator vanes. They give the pump better overall handling, consistent performance and instant priming (the delay between the moment when the intake is in contact with water and the moment when it actually starts pumping the water). This is the only way I have found to achieve life-scale jetsprint handling on a RC boat.

Ball steering. It is my new system where the servo is connected directly to a rotating shaft, instead of a pushrod. The advantage of this system is the simplicity - there are only 2 moving parts in total. Therefore, there are also less joints between the moving parts, which reduces the backlash. It uses a rubber O-ring as a seal around the steering shaft instead of a traditional rubber bellow. When you need to do some maintenance, for example change the servo, you only have to loosen the servo coupler and slide the shaft out. The range of movement of the shaft is exactly 60 degrees left and right, so there is no need to set the range of the servo movement on the transmitter.

Integrated ride plate. Many of my previous boats suffered from hopping when achieving higher speeds and this feature has finally solved all these problems. The ride plate lifts the stern of the boat and keeps the bow down, which stops the hopping effect completely. It is adjustable with a single screw - the same way as you would set trim tabs on a prop boat. In addition, it has four blades, which help with sharp cornering and prevent spin-outs. However, if you do not like this feature, you can just uninstall it and never use it.

Integrated watercooling. The water is pushed into a water channel in the Second stage, through a channel in First stage and the Housing, where a silicone tube is connected. Then the cooling loop goes back through the Housing and out of the boat from an outlet. The outlet is angled upwards so that you can control if the cooling works properly.

Integrated removeable intake grate. If your pump sucks grevel and you need to remove it from the impeller, just unscrew one screw and remove the intake grate to be able to access the impeller.

Rear installation.This jet drive is not glued into the hull from the inside like almost all other pumps. Instead, you cut a simple square hole (no difficult circle shapes!) and slide the pump into the hull from the rear. Therefore the thrust force of the pump pushes directly on the stern, instead of pulling the pump away from the glue. This method is much simplier than any other method I have tried. If you are wondering how exactly it works, check the manual listed above.

Performance: The jet drive achieves 3600g thrust at 20000RPM, my motor uses 1200W. However, it is important to understand that static thrust is not the only parameter that determines the performance of the pump: thrust decreases, as speed of your boat increases. Therefore, I also calculate the exhaust velocity using the Thrust equation (Force = mass flow * exhaust velocity). Exhaust velocity is the speed the water leaving the nozzle. Exhaust velocity of this jet drive is 11.9 m/s. The higher the velocity, the smaller the thrust drop at higher boat speed, therefore more top speed. I believe I have found a good balance between thrust and top speed with this pump.

Update 10. 5. 2020: Two parts of the steering assembly, Ball and Servo coupler, were changed for better strength and grip on the steering shaft.

Update 4.11.2020: These parts have been further reinforced.

Update 18.1.2021: The M-Jet was renamed to M-Jet 30.

Update 14.9.2021: A new folder Mods_for_M-Jet_30 was added to the files, including a single blade impeller design mod. It requires more testing on this pump, but was found to dramatically improve efficiency on a different pump.

D
davis-chris-e
Can you recommend a source for the 5mm rubber motor coupling? I can't find one anywhere. Thanks!
stepanmuller
stepanmuller
Hello, I used a KMB coupler and drilled through the 4mm hole with 5mm bit: https://kehrer-modellbau.de/en/KMB-JET28-Rev.-3/KMB-JET28-parts/KMB-high-load-shaft-coupling-OE-4-mm-OE-5-mm I used that one because I had one at the moment, but you can use any solid coupler as well, for example this one seems nice to me: https://www.amazon.com/Twidec-Flexible-Coupling-Connector-COUPLER-BU-5-6/dp/B07TWLGS37/ref=sr_1_24?dchild=1&keywords=5%2Bto%2B5mm%2Bmotor%2Bcoupler%2Bflexible&qid=1602053531&sr=8-24&th=1 Or this one: https://www.amazon.com/uxcell-Coupling-L20xD12-Coupler-Connector/dp/B07P6X9GSQ/ref=sr_1_3?dchild=1&keywords=5+to+5mm+motor+coupler&qid=1602052842&sr=8-3
D
delvecchio1971
I see you used the aquastar from hobby king, what esc did you use. Was it one of there qua ones with water cooling?
stepanmuller
stepanmuller
I used watercooled turnigy marine 120A ESC. Any watercooled ESC with at least 100 A rating will work, but the watercooling is definitely a necessity.
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lagrecak
Hi, have you thought of designing a backing bucket for your drive? Also is it possible to do a duel jet configuration? I'm not concerned with speed, just accuracy of the model im building.
stepanmuller
stepanmuller
Hi, I am not going to add any reverse bucket for this jet drive, since its goal is not scale accuracy but handling, functionality and simplicity. There is too little space for another servo and its linkage anyway. Dual jet configuration is totally possible. In order to be able to put the jets closer together, it would be advantagous to mirror one of them completely, so that both servos are positioned on the outside.
L
loccy
Can you recommend a 3D printed boat to use with this jet drive. Thanks!
stepanmuller
stepanmuller
Hi, unfortunately there is no 3D printable design of a hull that would fit this jet drive perfectly. I am using this hull which is not optimized for 3D printing: https://www.cgtrader.com/free-3d-print-models/hobby-diy/other/jetsprint-hull-for-rc-boats If you have some CAD skills, you should be able to modify it to make it better 3D printable. Alternatively, you can print the stock STLs of the hull, just in 3 pieces vertically and lay fibreglass on it to make it stronger and bond it together. Still, the best option would be to buy a physical ABS or fibreglass hull.
E
elynx
Don't buy if you don't have personal 3D printer. I did, and everything that could - failed. This *heavily* depends on quality of print. I had a local company print me parts, and outcome was less than stellar (not bad, just some slight rough places). On step 2 of assembly m3 nuts did not go all the way in, leaving 0.5 mm difference, so screw can not catch the nut. I could not take them out, and in process of trying to fit them further I broke out one of water exchange pipes. Well, this ended assembly for me, and after spending 60+ dollars (on model, print, steel, bearings and screws) and failing, I think I could not afford to go further with another print or different jet. Thus, I save myself a lot of money, since I would not be making boat. Overall, spent 60 bucks to lose a dream.
J
jeffjackson86
You are correct in saying its not worth it having someone print it for you. My local printer wanted $100 minimum for the print. I found a Creality Ender 3d printer on sale last week and got it $175 shipped to my house. The M-30 drive is printing right now! Now i can print the boat, the drive and anything else as many times as i want! Its not cost effective to pay someone else to do it.
Item rating
26 0
Recommended
Haven't assembled it yet, but printed beautifully.
Recommended
It is as far as I can tell is a well thought out design. I'm anxious to give it a go.
Recommended
Good quality model, many thanks
M-Jet 30 - 3D Printable Jet Drive for RC Boats
$10.00
 
Editorial License 
M-Jet 30 - 3D Printable Jet Drive for RC Boats
$10.00
 
Editorial License 
Response 94% in 2.2h

3D Model formats

  • Stereolithography (.stl) (2 files)5.67 MB
  • PDF (.pdf)5.41 MB

3D Model details

  • Publish date2020-04-17
  • Model ID#2368560
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